Viewing file:  Visitor.py (2.29 KB) -rw-r--r--
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########################################################################
#
# File Name: Visitor.py
#
#
"""
WWW: http://4suite.com/4DOM e-mail: support@4suite.com
Copyright (c) 2000 Fourthought Inc, USA. All Rights Reserved.
See http://4suite.com/COPYRIGHT for license and copyright information
"""
class Visitor:
def visit(self, node):
"""Default behavior for the visitor is simply to print an informational message"""
print "Visiting %s node %s\n"%(node.nodeType, node.nodeName)
return None
class WalkerInterface:
def __init__(self, visitor):
self.visitor = visitor
pass
def step(self):
"""Advance to the next item in order, visit, and then pause"""
pass
def run(self):
"""Continue advancing from the current position through the last leaf node without pausing."""
pass
class PreOrderWalker(WalkerInterface):
def __init__(self, visitor, startNode):
WalkerInterface.__init__(self, visitor)
self.node_stack = []
self.node_stack.append(startNode)
def step(self):
"""
Visits the current node, and then advances to its first child,
if any, else the next sibling.
returns a tuple completed, ret_val
completed -- flags whether or not we've traversed the entire tree
ret_val -- return value from the visitor
"""
completed = 0
ret_val = self.visitor.visit(self.node_stack[-1])
if (self.node_stack[-1].hasChildNodes()):
self.node_stack.append(self.node_stack[-1].firstChild)
else:
#Back-track until we can find a node with an unprocessed sibling
next_sib = None
while not next_sib and not completed:
next_sib = self.node_stack[-1].nextSibling
del self.node_stack[-1]
if next_sib:
self.node_stack.append(next_sib)
else:
if not len(self.node_stack):
completed = 1
return completed, ret_val
def run(self):
completed = 0
while not completed:
completed, ret_val = self.step()
#Set the default Walker class to the PreOrderWalker.
#User can change this according to preferences
Walker = PreOrderWalker
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